The present invention relates to a connector mounting structure and a connector mounting method used for electrical connection of terminals and a circuit board using a surface-mounting technology, and is particularly suitable for connectors mounted in a vehicle such as an automotive vehicle.
FIG. 3 is an exploded perspective view showing a prior art mounting structure for a surface-mounted connector, and FIG. 4 is an exploded perspective view showing another prior art mounting structure for a surface-mounted connector. It should be noted that no repeated description is given for elements common in FIGS. 3 and 4 by identifying them by the same reference numerals.
As shown in FIGS. 3 and 4, leading ends 21 of terminals 20 extending from a housing 11 are connected with lands 34 provided on an outer surface 33 of a board main body 31 of a printed circuit board 30 in conformity with the leading ends 21 by means of the so-called reflow soldering (40 in FIG. 3 identifies these soldered portions). Mounting structures 1A, 1B for the so-called surface-mounted connectors 10 for establishing the electrical connection of the terminals 20 and the lands 34 in this way have been known.
Since none of the terminals 20 of the surface-mounted connectors 10 is inserted into the board main body 31 of the printed circuit board 30 in both structures 1A, 1B, there are merits of enabling the terminals 20 to be arranged at narrow intervals and accordingly enabling the connector to be miniaturized. Thus, these mounting structures have been widely used in recent years.
However, in such a surface-mounted connector 10, an unnecessary force may act on the soldered portions 40 to peel them off when a mating connector (not shown) is inserted or withdrawn. Therefore, it is preferable to firmly fasten the housing 11 to the printed circuit board 30. On the other hand, the housing 11 of the surface-mounted connector 10 cannot be directly soldered to the printed circuit board 30 since being normally made of an insulating material such as a synthetic resin.
As a method of fastening such a surface-mounted connector 10 to the printed circuit board 30, there has been known a method according to which metallic plates 70 are attached at least to a bottom surface 14 of the housing 11 of the surface-mounted connector 10 and connected with metallic pads 90 provided on the outer surface 33 of the board main body 31 of the printed circuit board 30 by means of the so-called reflow soldering (90 in FIG. 3 identifies these soldered portions), thereby fastening the housing 1 to the printed circuit board 30 (see, for example, Japanese Unexamined Utility Model Publication No. H6-60066). Although the shape of the metallic plates 70 in FIG. 3 differs depending on a method of mounting the metallic plates 70 to the housing 11 in this publication, the flat metallic plates are shown here in order to simplify the description.
There is also known a method according to which screws 60 inserted through through holes 32 formed in the board main body 31 of the printed circuit board 30 are engaged with internally threaded holes 13 formed in left and right board mounting portions 12 of the housing 11 to fasten the housing 11 to the printed circuit board 30, for example, as in the structure 1B of FIG. 4 (see, for example, Japanese Unexamined Utility Model Publication No. H5-25680).
However, the structure 1A disclosed in the former publication leads to increased production costs since the metallic plates 70 are required extra. Further, fastening forces of the soldered portions 90 for firmly fastening the housing 11 of the surface-mounted connector 10 to the printed circuit board 30 may become insufficient with the passage of time. Therefore, there has been a durability problem of the surface-mounted connector 10 in such an application where vibrations and impacts are exerted particularly in a high-temperature environment such as in an automotive vehicle.
On the other hand, the structure 1B disclosed in the latter publication requires the high-precision production of the surface-mounted connector 10 and the printed circuit board 30 to position the housing 11 of the surface-mounted connector 10 on the printed circuit board 30 although being free from the above problem. Thus, productivity is reduced to lead to increased production costs.
In order to ensure a sufficient productivity, it is necessary to facilitate the positioning, which further requires a complicated and large-sized positioning structure or the like (although not shown in FIG. 4, such a positioning structure as to form recesses in the housing and accommodate nuts corresponding to the fastening screws in the recess later is disclosed, for example, in the latter publication). In this respect as well, production costs will be increased.
The complicated and large-sized positioning structure particularly hinders the miniaturization of the connector and the narrow arrangement of the terminals, whereby the above-mentioned original merits of the surface-mounted connector 10 cannot be employed.
If the above prior arts are simply combined, metallic plates are required extra, which leads not only to increased production costs, but also to a large problem in performance.
Specifically, a solder molten by reflowing (hereinafter, “molten solder”) generally displays a so-called self-alignment effect of automatically centering a metallic object placed on the molten solder by the action of surface tension, and this self-alignment effect is known to be proportional to the surface area of the molten solder.
Since the surface areas of the molten solders provided between the terminals and the lands are nonnegligibly large as compared to the surface areas of the molten solders provided between the metallic plates and the metallic pads, the self-alignment effect brought about by the surface tension of the molten solders provided between the terminals and the lands is hindered by the self-alignment effect brought about by the surface tension of the molten solders provided between the metallic plates and the metallic pads.
Accordingly, the operation of positioning the connector housing on the circuit board becomes more difficult only by simply combining the prior arts. For example, even if the housing is positioned on the circuit board such that the terminals are precisely placed on the lads, the terminals automatically move out of the lands by the self-alignment effect brought about by the surface tension of the molten solders provided between the metallic plates and the metallic pads. Thus, it becomes more difficult to fasten the housing at a specified position on the circuit board using, for example, screws.